CN103589010A - Microporous wave-absorbing material with low surface density and high tensile strength and preparation method - Google Patents

Abstract

The invention discloses a microporous wave-absorbing material with low surface density and high tensile strength and a preparation method thereof, belonging to the technical field of wave-absorbing materials. The invention solves the problems of high density, low mechanical properties and poor temperature resistance of existing microwave materials. The preparation method of the present invention is that rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent, plasticizer and absorbent are stirred evenly, and then through banburying and open milling, Vulcanize at 150-160°C and simultaneously foam for 25-35 minutes to obtain a microporous wave-absorbing material. The total thickness of the microporous wave-absorbing material prepared by the present invention is between 1.4-2.0mm, and the surface density is less than 1.7kg/m ² . Mechanical properties, the temperature resistance can reach 150°C, the average tensile strength is greater than 8.5MPa, and the minimum elongation at break is 360%.

Description

Microporous wave-absorbing material with low surface density and high tensile strength and preparation method thereof

technical field

The invention relates to a microporous wave-absorbing material with low surface density and high tensile strength and a preparation method thereof, belonging to the technical field of wave-absorbing materials.

Background technique

In the prior art, the patch-type wave-absorbing material is generally formed by mixing and rolling an adhesive and an absorbing agent (usually a magnetic material). By selecting different substrates and optimizing the formula design, the performance of the absorbing material can meet different needs. This kind of patch-type material absorbs waves with good uniformity, strong process controllability, stable material properties (especially electrical properties), and simple construction technology.

However, the existing patch-type absorbing materials generally have the disadvantage of high surface density. The surface density of the wave-absorbing sheet with a thickness of less than 1mm has mostly exceeded 3.0kg/m ² , the strength is generally around 4MPa, and the temperature resistance is average. Below 100°C, the mechanical performance and other requirements of aircraft and other equipment cannot be met.

Contents of the invention

The purpose of the present invention is to provide a low surface density high tensile strength wave absorbing material and a preparation method thereof in order to solve the problems of high surface density, low mechanical properties and poor temperature resistance of existing wave absorbing materials.

The microporous wave-absorbing material with low surface density and high tensile strength of the present invention includes rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent, plasticizer and absorbent; The mass ratio of described rubber, foaming agent and plasticizer is 100:(5-18):(15-25); Described foaming agent is azodicarbonamide (AC), modified azodicarbonamide Amide (ACPW) or N, N'-dimethylpentamethylenetetramine; The absorbent is micron-sized conductive carbon black, and the quality of the absorbent is rubber, zinc oxide, stearic acid, anti-aging agent, flow aid 30-40% of the total mass of additives, sulfur, accelerators, foaming agents and plasticizers.

Preferably, the mass of the absorbent is 5-18% of the total mass of rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent and plasticizer.

Preferably, the mass ratio of the rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur and accelerator is 100:5:2:2:1.5:2:1.

Preferably, the rubber is nitrile rubber or hydrogenated nitrile rubber.

Preferably, the anti-aging agent is N,N-nickel dibutyldithiocarbamate (NBC), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD), N - one or more of isopropyl-N'-phenyl-p-phenylenediamine (4010NA).

Preferably, the flow aid is granular fatty acid, granular fatty acid derivative or granular pentaerythritol stearate.

Preferably, the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide (CZ) or 2-mercaptobenzothiazole (MBT).

Preferably, the plasticizer is one or more of dibutyl phthalate, dioctyl phthalate, and diethyl phthalate.

The preparation method of the above-mentioned microporous wave-absorbing material with low surface density and high tensile strength comprises the following steps:

(1) After rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent, plasticizer and absorbent are stirred evenly, banburying is mixed evenly to obtain a mixture;

(2) refining the mixture obtained in step (1) to obtain uniform and stable raw materials;

(3) The uniform and stable raw material obtained in step (2) is vulcanized at 150-160° C. and simultaneously foamed for 25-35 minutes to obtain a microporous wave-absorbing material with low surface density and high tensile strength.

Preferably, in step (1), the banburying is banburying in an internal mixer within 85° C. for 10-15 minutes; in step (2), the banburying is in an open mixer for more than 20 times.

Beneficial effects of the present invention:

(1) The present invention uses micron-sized conductive carbon black as the absorber, so that the material has excellent wave-absorbing properties while having a lower surface density, and provides a certain reinforcing effect on the material, further increasing the mechanical properties of the material; and The foaming agent in the same temperature range as the vulcanization is used to make the material foam during the vulcanization during the preparation process, which ensures that the cells of the material are evenly distributed, and has a closed-cell structure, which realizes the low density and high strength of the material;

(2) The total thickness of the microporous wave-absorbing material prepared by the present invention is between 1.4-2.0mm, and the surface density is less than 1.7kg/m ² . The material has good wave-absorbing performance in a specific wave band, and has good temperature resistance Excellent mechanical properties, temperature resistance can reach 150°C, the average tensile strength is greater than 8.5MPa, and the minimum elongation at break is 360%;

(3) The preparation method of the present invention foams while vulcanizing the material, which not only ensures the structure of the microwave material, but also is simple, easy to implement, and low in cost, which is beneficial to large-scale production.

Description of drawings

Fig. 1 is the test graph of the plate reflectivity of the microporous wave-absorbing material material prepared by Example 1-3 of the present invention;

In Fig. 2, (a) is an optical microscope image of the cross section of the microporous absorbing material prepared in Example 1 of the present invention; (b) is an optical microscope image of the cross section of the microporous absorbing material prepared in Example 2 of the present invention picture.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with specific embodiments, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent requirements of the present invention.

The microporous wave-absorbing material with low surface density and high tensile strength includes 100 parts by weight of rubber, 5 parts by weight of zinc oxide, 2 parts by weight of stearic acid, 2 parts by weight of anti-aging agent, 1.5 parts by weight of flow aid, 2 parts by weight of sulfur, 1 part by weight of accelerator, 5-18 parts by weight of foaming agent, 15-25 parts by weight of plasticizer and absorbent; wherein the rubber is nitrile rubber 220 or hydrogenated nitrile rubber; The anti-aging agent is N, N-dibutyl dithiocarbamate nickel, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl p- One or more of phenylenediamines; the flow aid is granulated fatty acid, granulated fatty acid derivative or granulated isopentyl stearate, preferably granulated fatty acid derivative ZC-56 or granulated iso-stearate Pentaerythritol D-821; the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide or 2-thiol benzothiazole; the plasticizer is dibutyl phthalate, diphthalate One or more of octyl esters and diethyl phthalate; the blowing agent is azodicarbonamide, modified azodicarbonamide or N,N'-dimethylpentamethylenetetramine The absorbent is micron-scale conductive carbon black, and its quality is 30-40% of the total mass of rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent and plasticizer, Preferably 5-18% (according to the well-known in the field, default blowing agent has no residual calculation after forming the final product).

The preparation method of the microporous wave-absorbing material with low surface density and high tensile strength comprises the following steps:

(1) Physically stir rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent, plasticizer and absorbent, and then add them to the internal mixer and mix them uniformly. get the mixture;

The mass ratio of described rubber, zinc oxide, stearic acid, antioxidant, flow aid, sulfur, promotor, blowing agent and plasticizer is 100:5:2:2:1.5:2:1:(5 -18): (15-25), the blowing agent is azodicarbonamide, modified azodicarbonamide or N,N'-dimethylpentamethylenetetramine, and the absorbent is Micron-sized conductive carbon black, its quality is 30-40% of the total mass of rubber, zinc oxide, stearic acid, antioxidant, flow aid, sulfur, accelerator, blowing agent and plasticizer, preferably 5-18% % (according to the well-known in the field, the default blowing agent has no residual calculation after forming the final product);

(2) adding the mixture obtained in step (1) into the open mill, and rolling with the technology of wrapping rolls to obtain uniform and stable raw materials;

(3) Add the uniform and stable raw material obtained in step (2) into the mold, place the mold in a flat vulcanizer, vulcanize at 150-160°C and foam for 25-35 minutes at the same time, cut off the excess trim to obtain the low surface Microporous absorber with high density and high tensile strength.

In the present invention, rubber is nitrile butadiene rubber 220 or hydrogenated nitrile butadiene rubber, and antioxidant is N, N-nickel dibutyl dithiocarbamate, 2,2,4-trimethyl-1,2-dihydroquinoline One or more of morphine polymers, N-isopropyl-N'-phenyl-p-phenylenediamine, and the flow aid is granular fatty acid, granular fatty acid derivative ZC-56 or granular isopentyl stearate Tetrol D-821, preferably granular fatty acid derivative ZC-56 or granular stearic acid pentaerythritol D-821, the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide or 2-mercaptan benzothiazole, and the plasticizer is one or more of dibutyl phthalate, dioctyl phthalate, and diethyl phthalate.

In the step (1) of the present invention, the order of adding rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent, plasticizer and absorbent has certain requirements, according to field personnel It is known that sulfur and accelerators should be added at the end in order to prevent premature vulcanization due to excessive temperature.

In the step (1) of the present invention, in order to prevent the active ingredients of the auxiliary agent from being destroyed at high temperature, the temperature in the banburying process is preferably controlled within 85°C.

In the step (2) of the present invention, the rubber milling process cannot be fully milled evenly according to the existing three-pack two-roll process for rubber mixing due to the amount of rubber compounding. Therefore, the method of more than 20 times of milling is preferably used. .

The types of internal mixer and open mixer used in the present invention are selected according to the amount of prepared wave-absorbing material.

The die size of the flat vulcanizing machine used in the present invention is 200×200 mm ² or 300×300 ² mm, more preferably 300×300 ² mm, and the height of the cavity can be adjusted between 1.0-2.0 mm according to requirements.

The present invention will be further described in detail below in conjunction with the embodiments and the accompanying drawings.

Example 1

100g nitrile rubber 220, 5g zinc oxide, 2g stearic acid, 2gN,N-nickel dibutyldithiocarbamate, 1.5g granular fatty acid, 2g sulfur, 1gN-cyclohexyl-2-benzothiazolium Sulfonamide, 5g of azodicarbonamide, 15g of dibutyl phthalate and 40.5g of micron-sized conductive carbon black are added to the internal mixer and mixed evenly within 85°C to obtain a mixture; the mixture obtained by banburying is moved to Open the mill to obtain uniform and stable raw materials, then cut 62.0g of raw materials into a suitable size and put them into a 200×200 ² mm mold with a cavity height of 1.2mm, vulcanize and foam in a flat vulcanizer at 150°C for 25 minutes , to obtain the microporous absorbing material, the mechanical properties of the material are shown in Table 1.

Example 2

100g nitrile rubber 220, 5g zinc oxide, 2g stearic acid, 2g2,2,4-trimethyl-1,2-dihydroquinoline polymer, 1.5g granular fatty acid derivative ZC-56, 2g sulfur , 1g2-mercaptobenzothiazole, 10g modified azodicarbonamide, 20g dioctyl phthalate and 50.225g micron-sized conductive carbon black are added in the internal mixer and mixed evenly to obtain the mixture; The mixture obtained by refining is moved to an open mill and kneaded to obtain a uniform and stable raw material, then cut 65.0g of raw material into a suitable size and put it into a 200×200 ² mm mold with a cavity height of 1.5mm, vulcanized on a flat plate at 155°C Vulcanize and foam in the machine for 30 minutes to obtain a microporous wave-absorbing material. The mechanical properties of the material are shown in Table 1.

Example 3

100g of hydrogenated nitrile rubber, 5g of zinc oxide, 2g of stearic acid, 1g of N-isopropyl-N'-phenyl-p-phenylenediamine, 1g of N,N-nickel dibutyldithiocarbamate, 1.5g of granular Pentaerythritol stearate D-821, 2g sulfur, 1g 2-mercaptobenzothiazole, 15g N, N'-dimethylpentamethylenetetramine, 20g dioctyl phthalate, 3g phthalate Diethyl diformate and 50.3275g micron-sized conductive carbon black are added in the banbury mixer and mixed evenly to obtain the mixture; the mixture obtained from the banbury mixing is moved to the open mixer to obtain uniform and stable raw materials, and then 71.0 raw materials are cut Put it into a mold of 200×200 ² mm in a suitable size, the height of the mold cavity is 1.7mm, and vulcanize and foam in a flat vulcanizing machine at 155°C for 35min to obtain a microporous wave-absorbing material.

The microporous wave-absorbing material in Example 1-2 was made into a dumbbell sample with a width of 6 mm and an effective distance of 25 mm. The mechanical performance testing equipment is the SUNS electronic universal testing machine of Shenzhen Sansi Zongheng Technology Co., Ltd., and the test uses the GB/T528-1998 vulcanized rubber tensile method. The test results are shown in Table 1.

The mechanical property of the microporous wave-absorbing material of table 1 embodiment 1 and embodiment 2

The microporous wave-absorbing material obtained in Examples 1-3 was cut into standard samples of 180×180mm ² , the RCS testing equipment for the material was N-5244A of the Agilent vector network analyzer PNA-X series, and the testing method was the bow method. Tested for the 8-12GHz frequency band. The test results are shown in Figure 1. Slice and cut the material longitudinally to obtain a horizontal section, and use an electron microscope to photograph the section structure to obtain the foam size and foam distribution. The test results are shown in Figure 2.

Curve (a) in Fig. 1 is the plate reflectivity of the microporous wave-absorbing material of embodiment 1, as can be seen from curve (a), the absorption of the material in the 8-12GHz frequency range is lower than -6dB, and the peak value can reach - Below 30dB; Curve (b) in Fig. 1 is the plate reflectivity of the microporous wave-absorbing material of embodiment 2, as can be seen from curve (b), the absorption of material is all lower than -7dB in the 8-12GHz frequency range, and the peak value Can reach below-25dB; Curve (c) in Fig. 1 is the plate reflectivity of the microporous wave-absorbing material of embodiment 3, can find out from curve (c), material absorbs all lower than - 7.5dB, the peak can reach below -25dB.

Figure 2(a) is a cross-sectional optical microscope image of the microporous wave-absorbing material of Example 1. It can be seen from the figure that the foaming distribution of the material is relatively uniform, and the diameter of the closed cells is about 100 microns; Figure 2(b) It is a cross-sectional optical microscope image of the microporous microwave-absorbing material in Example 2. It can be seen from the figure that the foamed closed-cell aperture of the microwave material is mostly 100 microns, and the maximum value reaches more than 200 microns.

Apparently, the descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those of ordinary skill in the technical field, without departing from the principle of the present invention, some improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention .

Claims (10)

1. Microporous wave-absorbing material with low surface density and high tensile strength, characterized in that it includes rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent, plasticizer and Absorbent; The mass ratio of described rubber, whipping agent and plasticizer is 100:(5-18):(15-25); The foaming agent is azodicarbonamide, modified azodicarbonamide or N,N'-dimethylpentamethylenetetramine; Described absorbing agent is micron order conductive carbon black, and the quality of absorbing agent is 30-30-30% of the total mass of rubber, zinc oxide, stearic acid, antioxidant, flow aid, sulfur, promotor, whipping agent and plasticizer. 40%. 2. The microporous wave-absorbing material with low surface density and high tensile strength according to claim 1, wherein the quality of the absorbent is rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, 5-18% of the total mass of sulfur, accelerators, foaming agents and plasticizers. 3. the microporous wave-absorbing material of low surface density and high tensile strength according to claim 1, is characterized in that, the rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur and accelerator The mass ratio is 100:5:2:2:1.5:2:1. 4 . The microporous wave-absorbing material with low surface density and high tensile strength according to claim 1 , wherein the rubber is nitrile butadiene rubber or hydrogenated nitrile butadiene rubber. 5. The microporous wave-absorbing material with low surface density and high tensile strength according to claim 1, wherein the antioxidant is N, N-nickel dibutyldithiocarbamate, 2,2, One or more of 4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl-p-phenylenediamine. 6. The microporous wave-absorbing material with low surface density and high tensile strength according to claim 1, wherein the flow aid is granular fatty acid, granular fatty acid derivative or granular isopentyl stearate Tetrol. 7. The microporous wave-absorbing material with low surface density and high tensile strength according to claim 1, wherein the accelerator is N-cyclohexyl-2-benzothiazole sulfenamide or 2-mercaptan benzothiazole. 8. The microporous wave-absorbing material with low surface density and high tensile strength according to claim 1, wherein the plasticizer is dibutyl phthalate, dioctyl phthalate, o- One or more of diethyl phthalate. 9. The preparation method of the microporous wave-absorbing material with low surface density and high tensile strength according to any one of claims 1-8, characterized in that, comprising the following steps: (1) After rubber, zinc oxide, stearic acid, anti-aging agent, flow aid, sulfur, accelerator, foaming agent, plasticizer and absorbent are stirred evenly, banburying is mixed evenly to obtain a mixture; (2) refining the mixture obtained in step (1) to obtain uniform and stable raw materials; (3) The uniform and stable raw material obtained in step (2) is vulcanized at 150-160° C. and simultaneously foamed for 25-35 minutes to obtain a microporous wave-absorbing material with low surface density and high tensile strength. 10. The preparation method of the microporous wave-absorbing material with low surface density and high tensile strength according to claim 9, characterized in that, in step (1), the banburying is done in a banbury mixer within 85°C. Refining 10-15min, in step (2), described refining is to refine more than 20 times in the mill.

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